Ian - may I suggest it was possibly a leucistic Canada (a bird with partial white plumage) rather than a hybrid. I suggest this after recently banding my second leucistic Red-tailed Hawk in NY.
From: Ian Worley <[log in to unmask]>
To: VTBIRD <[log in to unmask]>
Sent: Sun, Feb 26, 2017 1:37 pm
Subject: [VTBIRD] Snow Goose x Canada Goose hybrid .. Lemon Fair WMA, Cornwall.
While beginning to count 2300 Canada Geese today in the flooded Lemon
Fair River flats west of West Street, Cornwall, I came upon a noticeably
large goose, as compared with the Canada Geese and one Snow Goose it was
foraging with. I was struck by its size, but it didn't really look like
any domestic goose with which I am familiar. I now think it is a Snow
Goose x Canada Goose hybrid.
As I was taking notes on its plumage, the ensemble of geese bolted as an
immature Red-tailed Hawk made a zooming pass. They landed about 0.3
miles up stream with other geese at a location I could not see well.
I saw the bird from right and left rear quarter view as it swam and when
it took flight. It was dark bodied above, and white below. The wings
were dark but the outer primaries were all white and very striking in
flight. My look at the neck was remembered poorly, though it definitely
was not white. The head was prominently pied in color, a mottling of
dark spots or blotches on a white field. I did not see the bill or feet
with any clarity.